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What is Mercury?

Mercury - known as "Hg" to chemists - is a naturally occurring element. It is a metal and conducts electricity. Liquid at room temperature, it combines easily with other metals and expands and contracts evenly with temperature changes. Because of these properties, mercury has been used in many households [PDF], medical and industrial products.

Although mercury performs many useful functions in our workplaces and homes, it is toxic and can impair the way we see, hear and function.

Mercury evaporates slowly. If spilled or improperly stored, this evaporation will cause continuous contamination of the air you breathe.

Mercury poisoning attacks the central nervous system in all humans. Children, especially those under the age of 6, are more susceptible to mercury poisoning. Each year, Indiana has about 300 reported cases of mercury poisoning involving children exposed to mercury from broken thermometers alone.

Less than a third of the mercury in the environment is naturally occurring. The majority is released through preventable human pollution. It enters the atmosphere, lakes and streams from coal burning for power generation, from industrial sources and by improper disposal of household products that contain mercury.

Improper mercury disposal includes: pouring it down drains, putting it in the trash and burning it in barrels and incinerators. These improper disposal methods can elevate mercury contamination to harmful levels.

When mercury seeps into lakes and waterways, it undergoes a natural chemical process and is converted to a more deadly form - methyl mercury. It then contaminates the food chain by building up in the tissue of fish and animals including those we eat. Numerous guides and information on safely consuming fish are available from the Indiana State Department of Health.

Facts about Mercury

Mercury is one of the 92 naturally occurring chemical "elements" that make up our physical world. Mercury has some unusual chemical and physical properties that make it a useful substance for a variety of electrical devices and other industrial applications.

Although mercury is a metal, it exists in a liquid state at room temperature. It generally occurs in nature as mercury sulfide (HgS), a reddish ore also know as cinnabar. Cinnabar was once used as a pigment and small figurines and reliefs also were carved from it.

Because mercury is a metal, it is an excellent conductor of electricity, and therefore is frequently used for electric switches. Mercury also is used in fluorescent, or mercury-vapor lights.

Because it readily expands and contracts as it gets warmer or cooler, it also is used in thermometers and thermostats.

Because it is liquid, but also is extremely dense and heavy compared to water and other liquids, it is used in barometers and other pressure detection devices.

Because mercury compounds can interfere with the growth of fungi, it also was previously used in latex paint to prevent mold.

Unfortunately, mercury is highly toxic to humans and other animals. In humans, it can effect the liver, kidney's, the central nervous system, or the brain. It is especially harmful to children and developing fetuses.

Because mercury also has a high surface tension which causes it to "bead up" and to absorb loose particles as it rolls along, it was in the past used to clean felt hats. However, "hatters," as the hat cleaners were known, eventually succumbed to mercury poisoning and suffered from dementia. Hence, the phrase "mad as a hatter." (and the character, the Mad Hatter, of Alice in Wonderland.)

Because mercury is a liquid, and also because it easily evaporates into the air, mercury can enter the environment very easily. Once it is in the environment, it can be difficult to clean up, can spread easily, and may persist for a long time.